Theme: Simply Catch- Feature Image Size on Category Post Page

First I want to say I have no .php or CSS experience. I am wanting to resize the image that shows up on the category post page like what is linked below. It is cutting off most of the image. I can’t use a different size image because of the feature image slider. So any suggestions on how to fix this will be great. Thank you. http://1stattackengineering.com/category/fast-attack-trucks-built/